Endoscopic instruments are introduced into the body of the patient, for example into the abdominal cavity, by way of a natural route or an artificial route, for example a cannula, with a view to performing an intervention on an internal organ. This may involve carrying out a biopsy of the organ or inserting a probe into the tissue at a precise location of the internal organ.
It may also involve inspecting a portion of the surface of the internal organ. The endoscopic instrument is then equipped, at its distal end, with a tool, for example a camera or an ultrasound probe. Depending on the circumstances, it may be necessary to ensure positioning and perfect immobility with respect to the internal organ, or it may be necessary to effect a relative movement of the distal end of the endoscopic instrument with respect to the internal organ, in a manner substantially parallel to an outer surface thereof, for example a scanning movement.
To obtain such a movement, the practitioner moves the endoscopic instrument manually, or with robotic assistance, by acting on the part of the endoscopic instrument arranged outside the body. However, such movements are not very precise, and they do not take account of the movements of the patient that induce a movement of the access route, nor of the inherent movements of the organ in the body of the patient.
It has been proposed to use means of immobilizing the organ, specifically a shaping tool which is pressed firmly onto the organ in an attempt to immobilize the latter. However, the immobility of the organ is not guaranteed. In addition, this type of immobilizing device is cumbersome and invasive.
It has also been proposed to perform automatic control of the position of the distal end of the endoscopic instrument relative to the internal organ by means of an on-board camera, the automatic control aiming to annul the relative movements of the distal end of the endoscopic instrument with respect to the internal organ. This method requires the use of real-time video acquisition, and also the use of a complex recursive and adaptive control algorithm.
It has also been proposed to perform automatic control in terms of force, which involves annulling the periodic component of the forces that are applied to the tool by the organ and that are attributable to the physiological movements of the internal organ.
It has also been proposed to equip the distal end of the endoscopic instrument with controlled means of movement which are arranged between the endoscopic instrument and the tool, in order to obtain a movement of the tool with respect to the endoscopic instrument, at least in directions transverse to a longitudinal axis of the end of the endoscopic instrument.
In a first method of use, the endoscopic instrument is immobilized when the tool is at a distance from the organ, and the means of movement are controlled in order to effect a relative movement of the tool with respect to the organ. However, the immobilization of the endoscopic instrument may generate stresses on the access route in the patient, and this may cause the latter discomfort. In addition, the inherent movements of the organ prevent any precise positioning or movement of the tool relative to the organ.
In a second method of use, the tool is brought into contact with the organ, and the endoscopic instrument is left free to move with the patient. However, an adherence may occur between the tool and the organ and cause resistance to the movement of the tool, thus preventing any movement of the latter with respect to the organ or, conversely, giving rise to sudden and uncontrolled slipping.
It is also known from document US 2011/0060227 to equip the distal end of the endoscopic instrument with a foot designed to bear on the internal organ. Shape-memory wires passing all the way through the endoscopic instrument allow the tool to be moved when the foot is bearing against the internal organ.